One cold December afternoon in 2001, I was travelling home on a slow-moving train from remote west Wales, having spent the day with a close friend who was recovering from a serious road accident, when I picked up a newspaper from the dirty floor of the carriage.

I had not seen a paper for several days and, still anxious about my friend, began to turn the pages desultorily until, at the bottom of an inside news page, my attention was arrested by an indistinct black-and-white photograph of writer WG Sebald. I read, for the first time, the sketchy details of his death in his car, which veered out of control on a foggy East Anglian road. It is not impertinent to suggest that the random manner and circumstances of his death and my discovery of it were highly Sebaldian.

That afternoon, I began to think of how Sebald, who was 57 when he died, might have written about something similar in one of his narratives and not-quite-fictions: how the sudden death of the writer and the publication of his photograph would have occasioned a series of literary, semi-autobiographical and quasi-philosophical reflections, rich in allusion and arcane references, with each reflection having the structural fluidity and unreliability of memory itself, moving back and forwards in time.

Sebald is, above all else, an elegist. His lost men, emigrants and wandering solitaries tell of lives ended abruptly or displaced by the inexorable forces of history over which they have no control. Many of the people he writes about exist now only in photographs or as names on gravestones and memorials.

In Campo Santo, this latest collection of fragments, essays and unfinished pieces, we find Sebald in Corsica. There, as usual, he takes a small room in a hotel, visits several museums that prompt the inevitable reflections about Napoleon and his extended family, and accompany him as he begins his lonely walks around the island. Soon we find him in the graveyard of Piana, reading the names of the long dead and worrying about overpopulation and who, if anyone, will honour, let alone remember, the dead of our teeming modern cities: Buenos Aires, Tokyo, Cairo, Lagos, Shanghai, Bombay.

Reading this, you are reminded of a scene in The Emigrants, the first of his books to be published in Britain for a general readership, when the narrator, who may or may not be Sebald, visits the Jewish cemetery in the small German town of Kissingen and begins to read out the names, many partially obliterated by dirt, on the headstones: Hamburger, Kissinger, Auerbach, Frank, Goldstaub, Blumenthal ... there was perhaps nothing, he thinks, 'the Germans begrudged the Jews so much as their beautiful names, and so intimately bound up with the country they lived in and with its language'.

The long aftermath of Germany's fascist experiment, both inside and outside the country, is Sebald's obsessive subject. But how to write about mourning and memory in a country that wants only to look forward? In his fascinating book, Air War and Literature, which was published here after his death, Sebald writes of his boyhood wanderings through bomb-destroyed cities and of how little was ever said or understood about the catastrophe that had unfolded in the Third Reich. The Germans around him, he said, were wilfully blind: when they turned to a take a backward view of the years 1930 to 1950, they were both 'looking and looking away', as if unable to comprehend the extent of their humiliation and defeat. They wished only to accept culpability and move on, to live only by forgetting - and certainly not linger on their own sense of suffering.

He returns to this subject again and again in the essays collected here in this book of last things. He wonders why the Allied destruction of so many German cities - Cologne, Hamburg, Dresden - never became, in Germany, a proper subject for novelists, for what he awkwardly calls 'literary depiction', as if the extremity and horror of what happened exceeded anything in the artistic imagination.

At school, Sebald remembers being taught more about Alexander the Great and Napoleon than of what had happened 'only 15 years in the past'. Even at university, 'I learned almost nothing of recent German history'.

Sebald himself did not live in Germany for most of his adult life. He lived in England, where he taught German literature at the University of East Anglia, took long walks, and wrote elliptical essays in German for a specialist readership.

Then, in 1996, The Emigrants, his story of four elderly men displaced by the German catastrophe, was published by the Harvill Press to unanimous acclaim. A great writer, as if from nowhere, was among us.

Sebald's is a distinctly pre-modern voice. To read him for the first time, with his fatigued high bourgeois European sensibility, his ignorance of popular culture, his sense of deep history and interdisciplinary learning, is almost to believe in cryonics or time travel: surely this man was not naturally of the present?

He writes in twilight mode; darkness is nearly always upon us. It is the middle of the day yet 'the gorge was sunk in darkness that I would not have thought possible,' he writes of returning to the Bavarian village of his childhood in Vertigo.

In The Emigrants, he writes of taking an early afternoon drive only to find that 'one might have indeed thought that night was falling, so low and inky black was the sky'.

Later in the same book, arriving in Manchester on a December afternoon, he observes that 'dusk was already falling at three o'clock'. In Campo Santo, ' the afternoon was already drawing to an end' when he enters his first museum.

And so it goes on, the effects and tropes repeated as the sense of sadness and loss accumulate. There can be something formulaic about Sebald: the unexpected darkness of mid-afternoon, the wandering narrators who suffer sudden seizures, the concentrated melancholy, the sly self-positioning, the deference to Kafka, the slow, meditative glide of his stately sentences. Nor will you find many jokes in his books.

Yet to read him at his best - not here, but in The Emigrants or Austerlitz - is to encounter a writer who, through much struggle, invented his own form and ways of writing about a subject that, for so many Germans, remained too painful ever to be properly and imaginatively addressed.